Elastomeric Adhesive Properties-Shear Strength, Shear Modulus, Creep, and Recovery

Three commercially available adhesives, approved for use in field glued floor systems, were evaluated for potential structural application in light frame wood buildings. All had adequate static shear strength for common floor and roof sheathing uses. Two were sufficiently rigid to generate useful composite action. One displayed relative creep compatible with wood structural design practice but two had excessive relative creep. The adhesive with good creep properties also had good recovery properties. The other two had poor recovery properties. One adhesive that had good shear strength in a conventional block shear test would not consistently sustain stress as low as 25 psi for more than four days. All tests were conducted on bonded wood specimens at 70 F (21 C) and 12% EMC

Low Temperature Gas Desulphurisation Using Mixed Cobalt-Zinc Oxides

The hydrogen sulphide absorption capacity of a range of mixed cobalt-zinc oxides was determined using a continuous flow microreactor. The mixed oxides were prepared by the thermal decomposition of hydroxycarbonate precursors. The precursors were synthesized by the coprecipitation method using the mixed metal nitrates and ammonium or sodium carbonate. X-Ray diffraction studies of the precursors synthesized from ammonium carbonate revealed that at low cobalt loadings hyrozincite, Zn5(C03)2(OH)6, was present as the predominant phase and spherocobaltite, COCO3, as the minor phase. At cobalt loadings ≥50% spherocobaltite was observed as the major phase. However, the Co/Zn 100/0 precursor revealed only the presence of a metastable phase, Co(CO3)0.5(OH)1.0.0.1H2O which had been previously identified by Porta et al. UV-VIS-NIR diffuse reflectance spectroscopy revealed that the cobalt was present in the 2+ oxidation state in an octahedral environment in all the precursors. When sodium hydrogen carbonate was used as the precipitating agent sodium zinc carbonate, Na2Zn3(CO3)4!3H2O, was formed. This was believed to be an intermediate in the formation of hydrozincite. For the Co/Zn 30/70 loading the pH used during the coprecipitation altered the predominant phase structure found in the final precursor. The major phase obtained on calcination of the precursors with a Co/Zn ratio ≤30/70 was ZnO with the a 'cobalt oxide type' phase (taken to be CO3O4) present as a minor phase. As the cobalt loading was increased this situation was reversed and CO3O4 became the major phase. Varying the temperature at which the precursor was calcined to the oxide revealed that the highest surface area was achieved when the precursor was calcined at ca. 200°C. An X-Ray photoelectron study of the oxides calcined at 350°C revealed that only Co3+ and Zn2+ ions were present at the surface suggesting the presence of a 'surface spinel', ZnCo2O4. Segregation of cobalt to the surface was observed. This segregation was believed to be determined during the synthesis of the precursor and was carried through to the oxide. The reaction of the mixed oxides with H2S was restricted to ca. 3 monolayers on average, based on calculations from surface areas, and is therefore largely confined to the surface of the oxides. For the oxides calcined at ≥350°C the linear relationship observed between the surface area and the sulphur uptake suggested that lattice diffusion played a major role in the rate determining step, the main role of the cobalt being to increase the surface area. The oxides calcined ≤250°C showed no correlation between surface area and sulphur uptake. It is likely that both pore and lattice diffusion contributed to the rate of sulphur uptake in these oxides. The oxides with a Co/Zn ratio of 100/0 were found to be the best sulphur absorbents. Calculations indicated that a bulk reaction had taken place in these oxides. Transmission electron micrographs of the mixed oxides before and after sulphidation revealed the presence of a sheet-like material which became more prevalent the more the mixed oxide was sulphided. Electron energy loss spectroscopy indicated that these sheet-like regions were predominantly zinc in composition

Primary Creep in Douglas-Fir Beams of Commercial Size and Quality

Primary creep of nominal 4- x 4-inch Douglas-fir beams of No. 2 grade was measured at four levels of stress, at 12% wood moisture content.Equations are presented for deflection and relative creep at the four stress levels. Results show relative creep to be nearly independent of stress level, with some evidence that relative creep shows a negative correlation with wood elastic modulus

Environmental dependence of X-ray and optical properties of galaxy clusters

Galaxy clusters are widely used to constrain cosmological parameters through their properties, such as masses, luminosity, and temperature distributions. One should take into account all kind of biases that could affect these analyses in order to obtain reliable constraints. In this work, we study the difference in the properties of clusters residing in different large-scale environments, defined by their position within or outside of voids, and the density of their surrounding space. We use both observational and simulation cluster and void catalogues, i.e. XMM Cluster Survey (XCS) and redMaPPer clusters, Baryon Oscillation Spectroscopic Survey (BOSS) voids, and Magneticum simulations. We devise two different environmental proxies for the clusters and study their redshift, richness, mass, X-ray luminosity, and temperature distributions, as well as some properties of their galaxy populations. We use the Kolmogorov–Smirnov two-sample test to discover that richer and more massive clusters are more prevalent in overdense regions and outside of voids. We also find that clusters of matched richness and mass in overdense regions and outside voids tend to have higher X-ray luminosities and temperatures. These differences could have important implications for precision cosmology with clusters of galaxies, since cluster mass calibrations can vary with environment

Impact of the Physical Cellular Microenvironment on the Structure and Function of a Model Hepatocyte Cell Line for Drug Toxicity Applications

It is widely recognised that cells respond to their microenvironment, which has implications for cell culture practices. Growth cues provided by 2D cell culture substrates are far removed from native 3D tissue structure in vivo. Geometry is one of many factors that differs between in vitro culture and in vivo cellular environments. Cultured cells are far removed from their native counterparts and lose some of their predictive capability and reliability. In this study, we examine the cellular processes that occur when a cell is cultured on 2D or 3D surfaces for a short period of 8 days prior to its use in functional assays, which we term: “priming”. We follow the process of mechanotransduction from cytoskeletal alterations, to changes to nuclear structure, leading to alterations in gene expression, protein expression and improved functional capabilities. In this study, we utilise HepG2 cells as a hepatocyte model cell line, due to their robustness for drug toxicity screening. Here, we demonstrate enhanced functionality and improved drug toxicity profiles that better reflect the in vivo clinical response. However, findings more broadly reflect in vitro cell culture practises across many areas of cell biology, demonstrating the fundamental impact of mechanotransduction in bioengineering and cell biology